Data from: Evaluation of Xpert® MTB/RIF assay in induced sputum and gastric lavage samples from young children with suspected tuberculosis from the MVA85A TB vaccine trial

Objective: Diagnosis of childhood tuberculosis is limited by the paucibacillary respiratory samples obtained from young children with pulmonary disease. We aimed to compare accuracy of the Xpert® MTB/RIF assay, an automated nucleic acid amplification test, between induced sputum and gastric lavage samples from young children in a tuberculosis endemic setting. Methods: We analyzed standardized diagnostic data from HIV negative children younger than four years of age who were investigated for tuberculosis disease near Cape Town, South Africa [2009–2012]. Two paired, consecutive induced sputa and early morning gastric lavage samples were obtained from children with suspected tuberculosis. Samples underwent Mycobacterial Growth Indicator Tube [MGIT] culture and Xpert MTB/RIF assay. We compared diagnostic yield across samples using the two-sample test of proportions and McNemar’s χ2 test; and Wilson’s score method to calculate sensitivity and specificity. Results: 1,020 children were evaluated for tuberculosis during 1,214 admission episodes. Not all children had 4 samples collected. 57 of 4,463[1.3%] and 26 of 4,606[0.6%] samples tested positive for Mycobacterium tuberculosis on MGIT culture and Xpert MTB/RIF assay respectively. 27 of 2,198[1.2%] and 40 of 2,183[1.8%] samples tested positive [on either Xpert MTB/RIF assay or MGIT culture] on induced sputum and gastric lavage samples, respectively. 19/1,028[1.8%] and 33/1,017[3.2%] admission episodes yielded a positive MGIT culture or Xpert MTB/RIF assay from induced sputum and gastric lavage, respectively. Sensitivity of Xpert MTB/RIF assay was 8/30[26.7%; 95% CI: 14.2–44.4] for two induced sputum samples and 7/31[22.6%; 11.4–39.8] [p = 0.711] for two gastric lavage samples. Corresponding specificity was 893/893[100%;99.6–100] and 885/890[99.4%;98.7–99.8] respectively [p = 0.025]. Conclusion: Sensitivity of Xpert MTB/RIF assay was low, compared to MGIT culture, but diagnostic performance of Xpert MTB/RIF did not differ sufficiently between induced sputum and gastric lavage to justify selection of one sampling method over the other, in young children with suspected pulmonary TB.研究目的：儿童肺结核（childhood tuberculosis）的诊断常受限于肺病患儿获取的呼吸道标本中结核分枝杆菌菌量稀少。本研究旨在对比结核病流行地区内，低龄儿童的诱导痰（induced sputum）与洗胃样本（gastric lavage samples）在Xpert® MTB/RIF检测（Xpert® MTB/RIF assay，全自动核酸扩增试验）中的诊断准确性。 研究方法：本研究分析了2009年至2012年间，南非开普敦附近地区疑似结核分枝杆菌感染的4岁以下HIV阴性儿童的标准化诊断数据。研究人员从疑似肺结核患儿中采集成对的连续诱导痰标本与清晨洗胃样本。所有标本均接受分枝杆菌生长指示管（Mycobacterial Growth Indicator Tube，MGIT）培养与Xpert® MTB/RIF检测。本研究采用两样本率比较检验与麦克尼马尔卡方（McNemar’s χ2）检验对比不同标本的诊断检出率，并通过威尔逊得分法（Wilson’s score method）计算灵敏度与特异度。 研究结果：本研究在1214次住院就诊中对1020名儿童进行了肺结核评估，并非所有儿童均采集了4份标本。在4463份标本中，57份（1.3%）经分枝杆菌生长指示管培养检出结核分枝杆菌阳性；4606份标本中，26份（0.6%）经Xpert® MTB/RIF检测呈阳性。诱导痰标本中，2198份样本里有27份（1.2%）呈阳性（任意一项检测：Xpert® MTB/RIF检测或MGIT培养）；洗胃样本中，2183份样本里有40份（1.8%）呈阳性。在诱导痰标本对应的1028次住院就诊中，19次（1.8%）检出MGIT培养或Xpert® MTB/RIF检测阳性；洗胃标本对应的1017次住院就诊中，33次（3.2%）检出上述两项检测阳性。对于两份诱导痰标本，Xpert® MTB/RIF检测的灵敏度为8/30（26.7%；95%置信区间（confidence interval, CI）：14.2~44.4）；对于两份洗胃样本，其灵敏度为7/31（22.6%；11.4~39.8，p=0.711）。对应的特异度分别为893/893（100%；99.6~100）与885/890（99.4%；98.7~99.8，p=0.025）。 研究结论：相较于MGIT培养，Xpert® MTB/RIF检测的灵敏度较低，但在疑似肺结核的低龄儿童中，诱导痰与洗胃样本的Xpert® MTB/RIF检测诊断性能无显著差异，不足以支持优先选择其中一种采样方式。